private void AvoidDirtyRead()
{
// if disk are exclusive don't need check dirty read
if (_disk.IsExclusive)
{
return;
}
_log.Write(Logger.CACHE, "checking disk to avoid dirty read");
// empty cache? just exit
if (_cache.CleanUsed == 0)
{
return;
}
// get ChangeID from cache
var header = _cache.GetPage(0) as HeaderPage;
var changeID = header == null ? 0 : header.ChangeID;
// and get header from disk
var disk = BasePage.ReadPage(_disk.ReadPage(0)) as HeaderPage;
// if header change, clear cache and add new header to cache
if (disk.ChangeID != changeID)
{
_log.Write(Logger.CACHE, "file changed from another process, cleaning all cache pages");
_cache.ClearPages();
_cache.AddPage(disk);
}
}
/// <summary>
/// Checkpoint is a safe point to clear cache pages without loose pages references.
/// Is called after each document insert/update/deleted/indexed/fetch from query
/// Clear only clean pages - do not clear dirty pages (transaction)
/// </summary>
public void CheckPoint()
{
if (_cache.CleanUsed > _cacheSize)
{
_cache.ClearPages();
}
}
/// <summary>
/// Checkpoint is a safe point to clear cache pages without loose pages references.
/// Is called after each document insert/update/deleted/indexed/fetch from query
/// Clear only clean pages - do not clear dirty pages (transaction)
/// Return true if cache was clear
/// </summary>
public bool CheckPoint()
{
if (_cache.CleanUsed > _cacheSize)
{
_log.Write(Logger.CACHE, "cache size reached {0} pages, will clear now", _cache.CleanUsed);
_cache.ClearPages();
return(true);
}
return(false);
}
/// <summary>
/// Test if cache still valid (if datafile was changed by another process reset cache)
/// Returns true if file was changed
/// [Thread Safe]
/// </summary>
private bool DetectDatabaseChanges()
{
// if disk are exclusive don't need check dirty read
if (_disk.IsExclusive)
{
return(false);
}
// empty cache? just exit
if (_cache.CleanUsed == 0)
{
return(false);
}
_log.Write(Logger.CACHE, "checking disk to detect database changes from another process");
// get ChangeID from cache
var header = _cache.GetPage(0) as HeaderPage;
var changeID = header == null ? 0 : header.ChangeID;
// and get header from disk
var disk = BasePage.ReadPage(_disk.ReadPage(0)) as HeaderPage;
// if disk header are in recovery mode, throw exception to datafile re-open and recovery pages
if (disk.Recovery)
{
_log.Write(Logger.ERROR, "datafile in recovery mode, need re-open database");
throw LiteException.NeedRecover();
}
// if header change, clear cache and add new header to cache
if (disk.ChangeID != changeID)
{
_log.Write(Logger.CACHE, "file changed from another process, cleaning all cache pages");
_cache.ClearPages();
_cache.AddPage(disk);
return(true);
}
return(false);
}